When manufacturing rubber products such as tires, rubber hose, or the like, kneading materials that include various constituent materials such as, for example, raw rubber, carbon black, and the like, are placed in a closed-type rubber kneader and kneaded. As a result of this kneading, each of the constituent materials is uniformly dispersed within the raw rubber, and the viscosity of the kneading materials is reduced to a constant viscosity. Two rotors are disposed in parallel within a chamber in the closed-type rubber kneader, and these rotors are rotated to knead the kneading materials. The kneading materials are rotated about the rotor shaft as center, and are kneaded by a shear force applied between the rotor and the inner wall face of the chamber.
There are various types of closed-type rubber kneader with different specifications of rotor, rotor drive motor, chamber, and the like. In order to carry out kneading efficiently, it is desirable that a kneader suitable for the kneading materials is selected and used, or if an existing rubber kneader is used, preferably the kneading is carried out under conditions suitable for the kneading materials.
The method using the power-time curve of the kneader is known as a means for evaluating the state of kneading of a closed-type rubber kneader (for example, see Kazuo NISHIMOTO, Masaaki URABE, Tetsuo AKIYAMA: “Spectral Analysis of Power-Time Curve”, Nippon Gomu Kyokaishi, Vol. 65, No. 8, pp 465-472, 1992, hereinafter referred to as “Nishimoto”). However, the method in this document is mainly for determining the state of kneading at a certain point in time, and it is not for evaluating the kneading efficiency of a closed-type rubber kneader.
Therefore, Nishimoto is not directly of reference for determining what specification of kneader is suitable for efficiently kneading certain kneading materials, or, for determining under what conditions they can be efficiently kneaded. Accordingly, there is a demand for a method capable of evaluating simply and accurately the kneading efficiency of a closed-type rubber kneader.